Table 2.

Main characteristics of the studies included in this review.

Authors	N	Exercise Protocol	Measurements
[63]	33 elderly Japanese men (67–72 years)	Randomized crossover tria l5-week endurance exercise, 3 times/week The intensity increased from 60 to 75% VO2peak	16s rRNA (V3-V4) CRF test Brief self-administered diet history questionnaire MRI Lipid profile, HbAC1 Blood pressure Cardio-ankle vascular index
[66]	373 men between 78–98 years	Observational study	Accelerometer 16s rRNA (V4) FFQ
[65]	70 community-dwelling older adults + 28 physically active senior volunteers (orienteers) aged > 65 years	Observational study	Gastrointestinal symptom rating scale (GSRS) Hospital anxiety and depression scale (HADS) FFQ Franding–Grimby activity scale (assess PA level) Next-generation sequencing (NGS)
[68]	897 subjects aged > 60 years	Observational study. Detected the effect of exercise on the gut microbiota in elderly individuals by using the data from the American Gut Project	Used the data obtained from the American Gut Project 16s rRNA (V4)
[64]	12 physically inactive older women aged > 60 years	Randomized controlled trial 8-week exercise training of aerobic and resistance exercise 60’ sessions 4x/week of aerobic + resistance exercise	IPAQ Mini-mental state examination (MMSE) Health examination Height, body weight flexibility, strength, and balance Fasted glucose, total cholesterol. LPL. HDL HBA1c 16s rRNA (V4)
[67]	100 subjects 55–74 years	Observational study	Accelerometer BMI 16s rRNA (V3-V4) FFQ
[61]	15 participants (95% men) aged 50–75 years	Randomised Trial 24-week aerobic + resistance exercise intervention 2 weeks: low intensity (20–30′ treadmill walking at 30–40% VO2max + 3 × 8 reps at 40–50% 1-RM) increasing to 50′ by the end of 12 weeks at 40–50% VO2max + 60–70% 1-RM After 13 weeks: randomized to continue moderate or high intensity exercise (60–70% VO2max + >80% 1-RM)	VO2max 16s rRNA (V3-V4) Gas chromatography to assess stool SCFA 3-day dietary survey